Investigating Anomalous Growth of Platinum Particles during Accelerated Aging of Diesel Oxidation Catalysts

Abstract When Pt catalysts are aged in air at 800 °C, we see significant growth of Pt particle sizes. The particle size distributions in the aged catalysts are usually bimodal, with some very large particles coexisting with smaller particles. Here we investigate the origins of these anomalous particle size distributions and relate them to the vapor phase transport of PtO2 under oxidizing conditions. Our results suggest that the emission of PtO2 from the catalyst into vapor phase could be a cause for the anomalous growth of Pt particles observed during high temperature aging. We show that supports such as ceria that can trap Pt ions cause a suppression of vapor phase transport, while the alumina and the MgAl2O4 spinel supports are unable to trap the Pt ions leading to the formation of abnormally large Pt particles.